2017 Mar 14G van Belle - NPOI1

NPOI: Visible Light Operations, Upgrades

Gerard van Belle (Lowell Observatory)

2017 Mar 14G van Belle - NPOI2

Recent Meeting of Interferometry Minds

Theo tenBrummelaar(GSU)Director,CHARA Array

Don Hutter(USNO)Director,NPOI(retiringApr 30)

Gerard vanBelle (Lowell)Director,NPOI(as of May 1)

2017 Mar 14G van Belle - NPOI3

Funded Upgrade: Palantir $3.26M project to add 3×1.0-m

CDK1000 telescopes to NPOI Supported by the NRL to Lowell

Observatory (PI: G. van Belle) A Quenyan (Elvish) word meaning

‘far-seeing’ “Precision Array of Large

Aperture New Telescopes for Image Reconstruction”

2017 Mar 14G van Belle - NPOI4

Infrastructure Reuse Vacuum feed system

Up to 3 beams per arm Combinations of 6 beams selectable

at array center Significant facility infrastructure

investment Elevator cans, lizard heads, vacuum

beam pipes, foundations Rule of thumb: 1 λ of wavefront

distortion for every 5-10m of air propagation in a lab setting

siderostat

lizardhead

elevatorcan

vacuum pipevacuum pipe

2017 Mar 14G van Belle - NPOI5

Large Apertures for NPOI New 1.0 m model

(CDK1000) from PlaneWave Instruments Robust, turnkey operations CDK700 proven with

MINERVA and other projects

Coudé train to be added to unmodified telescope

Breadboard for AO 70× increase in collecting

area: Δm of up to +4.5mag

2017 Mar 14G van Belle - NPOI6

Large Apertures:Rapid Relocation Apertures will be easily

relocatable throughout site Enables ‘compact’ (~8m baselines) Enables longest (~432m) baselines Daytime repositioning

Simple yet effective technology ‘Horse trailers’ Large kinematic pads Proven at IOTA, VLTI

VLTIParanal, ca. 2010

IOTAMt. Hopkins, 1997

2017 Mar 14G van Belle - NPOI7

Implementation at NPOI Current strawman design Flatbed trailer Standard 16’ AstroHaven

dome Telescope lifted by trailer

for relocation On-station, telescope

isolation from trailer on kinematic legs / piers

2017 Mar 14G van Belle - NPOI8

Other Large Apertures Lightweight 1.4-m

carbon fiber reinforced plastic Remain under

development at CMA

1.8-m Keck ‘outrigger’telescopes No longer

available for NPOI1.4-m CFRP 1.8-m ‘Outrigger’

2017 Mar 14G van Belle - NPOI9

Initial Layout (I) Compact array Observing large

(~50mas) objects Roughly 8-32m

baselines Medium, wide array Observations of

~0.25mas objects Baselines at 100, 200,

430m

NPOI Palantir compact array configuration

2017 Mar 14G van Belle - NPOI10

Initial Layout (II) Wide array 432m will be longest

optical baseline in the world

December 2017 delivery for 3×CDK1000s

NPOI Palantir wide array configurations

2017 Mar 14G van Belle - NPOI11

The Other Problem Two kinds of fringes Those that are easy to see Those that are interesting

Signal-to-noise goes as NV2

Mozurkewich’s law:

“Determine which fringes are easy to see, and declare they are therefore interesting”

→ unfortunately does not apply here

0.0

0.1

0.2

0.3

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0.5

0.6

0.7

0.8

0.9

1.0

0.0 5.0 10.0 15.0Angular Size (mas)

Vis

ibili

ty S

qu

ared

StarGeosat

Easy to see

All the good stuff is here

StarComplexobject

2017 Mar 14G van Belle - NPOI12

Challenge: How to Collect Interesting Fringes? Solution: Wavelength-Baseline Bootstrapping Track in the near-infrared with short baselines Image in the visible with medium, long baselines

Also takes advantage of the very red color of targets

2017 Mar 14G van Belle - NPOI13

Wavelength-Baseline Bootstrapping Tech demo to use real NPOI

configuration Longest ‘short’ baseline is

~8m Longest possible baseline is

39.9m (with 6 stations) Challenge: tracking well

enough in near-IR SNR~50-100 @ K, short

baselines For SNR ~3 @ V, long

baseline 0.001

0.010

0.100

1.000

0 10 20 30 40 50 60 70Angular Size (mas)

Frin

ge c

ont

rast

V-band: 8.5-mV-band: 39.9-mK-band: 8.5-mK-band: 39.9-m

2017 Mar 14G van Belle - NPOI14

DCT Speckle Imaging Speckle imaging

Recovers full diffraction-limited resolution of Lowell’s 4.3-m Discovery Channel Telescope

λ/D ≈ 25mas Sensitive: limiting mV ≈ 15.5 Visitor instrument: Dual-channel Stellar

Speckle Imager (DSSI) Also goes to WIYN, Gemini-N, Gemini-S

Stellar sources: binaries First DCT paper: Horch et al. 2015 ~1,100 sources over ~10 nights

Great telescope pointing

2017 Mar 14G van Belle - NPOI15

DSSI upgrade Dual-channel to quad-channel with

wave-front sensing: QWSSI

Includes option for aperture mask

Provides low-order spatial frequency information to be combined with NPOI

Leverages off-the-shelf filters

Simultaneous wavefront sensing Demonstrated at Maui AEOS Significantly improved SNR,

contrast ratios

Questions?

Paul Signac, “Port St. Tropez”, 1899